One of the niceties of linux distros like Ubuntu is that you can ‘mount’ ISO files. An ISO file, or ISO image, is an archive of a CD or DVD. By mounting an ISO file, you can read the data as though you inserted the CD into your computer. Ubuntu will even regard it as a CD (or DVD) so that games, video players, etc. think that they are reading from an actual CD (or DVD).
To mount the ISO, you first need a directory to mount to. Create this directory anywhere on your file system. ie:
sudo mkdir /media/iso
Once that’s done, we mount the ISO:
sudo mount -o loop [/path/to/iso/image/file] /media/iso
And voila, your ISO image is mounted. Your programs should now see a new CD/DVD device for you to use.
When you’re done with the iso, you can unmount it by typing:
sudo umount /media/iso
Note that you can mount as many ISO files at a time as you like – useful if you’re playing a game which requires multiple CDs.